The antibiotic susceptibilities of Xanthomonas maltophilia and their relation to clinical management.

An increase in recovery of Xanthomonas maltophilia from clinical specimens at our institutions prompted, amongst other measures, an investigation of the antibiotic susceptibility patterns of the organism. Fifty-five consecutive first isolates of Xanthomonas maltophilia were obtained and antimicrobial susceptibility tests were carried out by the agar dilution method. Trimethoprim/sulfamethoxazole was the most active antimicrobial agent (94% susceptible), with 71% susceptible to ticarcillin/clavulanic acid, 56% susceptible to ciprofloxacin and 49% susceptible to ceftazidime. Amoxycillin/clavulanic acid and imipenem were inactive (0% susceptible), while aminoglycosides were effective against only 7% of isolates. Potentiation was observed with both the combination of trimethoprim and sulfamethoxazole and the combination of ticarcillin and clavulanic acid. Familiarity with the antibiotic susceptibility pattern of Xanthomonas maltophilia as well as the potential shortcomings of the in vitro susceptibility data are important in the effective clinical management of Xanthomonas maltophilia infections.

Paecilomyces variotii in peritoneal dialysate.

Four cases of peritonitis caused by the filamentous fungus Paecilomyces variotii in patients on continuous ambulatory peritoneal dialysis are reported. Removal of the Tenckhoff catheter and antifungal chemotherapy led to resolution of symptoms in all cases. Possible contaminating events are discussed, and reported infections with P. variotii are reviewed.

Diphtheria: another risk of travel.

A 19-year-old woman presented with cellulitis of her foot 10 days after returning from Bali. Swabs of a central necrotic area grew toxigenic Corynebacterium diphtheriae biotype gravis. The patient was treated with parenteral penicillin and made a complete recovery. Diphtheria immunisation should be regularly updated for travellers to the tropics. Clinical and laboratory recognition of this infection is essential for appropriate public health measures to be undertaken.

Detection of teichoic acid antibodies in Staphylococcus aureus infections.

A commercially available agar gel diffusion (AGD) assay was used to investigate the teichoic acid antibody (TAA) response in 183 patients with proven Staphylococcus aureus (SA) infections. Two control groups were also investigated. One consisted of 100 hospitalized patients with a variety of medical and surgical conditions other than SA infection and the other consisted of 116 healthy hospital staff members. The sensitivity of the AGD assay varied markedly depending on the site of infection in the patients with proven SA infections. All patients with SA endocarditis developed positive TAA titres (greater than or equal to 1:4), although more than one third of these were initially negative. In patients with chronic osteomyelitis or septic arthritis, 41% had positive TAA titres, whereas no positive titres were detected in patients with acute osteomyelitis or septic arthritis. Lower rates of positive TAA titres were found in patients with deep abscesses (27%), pneumonia (14%) and post-operative infections (9%), but no positive titres occurred in patients with acute uncomplicated bacteremia, cellulitis or meningitis. In 100 hospitalized control patients, no positive titres were detected, and only 1 of 116 (0.9%) healthy hospital staff controls was positive. Suggested guidelines for the use of the AGD assay are discussed.

Antibiotic-induced release of endotoxin in chronically bacteriuric patients.

A novel in vivo model for the study of antibiotic-induced release of endotoxin from gram-negative bacteria is described. The model uses the chronically colonized urinary tracts of patients whose spinal cords have been injured. At baseline, the organisms were present in the range of 1 x 10(3) to 2 x 10(7) CFU/ml, and the concentration of endotoxin ranged from 2 x 10(-1) to 1 x 10(3) ng/ml in 44 studies. In 10 control studies, the concentration of endotoxin and the numbers of viable gram-negative bacteria over time changed by an average of less than 0.15 log10 units from the baseline values. At 2 h after antibiotic administration, the average decrease in CFU was 0.93 log10 units, and because antibiotics cause the release of endotoxin, an average increase in endotoxin concentration of 0.59 log10 units was noted in 21 studies with susceptible bacteria. Similar changes in response to antibiotic exposure were seen in studies with susceptible Pseudomonas bacteria in comparison with those seen in studies with susceptible members of the family Enterobacteriaceae. These results provide evidence that this novel model may be useful for comparing the effects of antibiotics with different modes of action, both as single agents and in combination, on the concentration of endotoxin in relation to changes in the numbers of bacteria, under conditions of bacterial replication and antibiotic exposure more closely resembling those found in vivo than is possible in other models.

Quantitative Limulus lysate assay for endotoxin and the effect of plasma.

The effects of plasma and chromogenic substrate on the kinetics of the endotoxin-activated Limulus amoebocyte lysate (LAL) assay were determined. A linear correlation was observed between the rate of development of turbidity (optical density 405) with the LAL reagent and the concentration of endotoxin over a four log ten-fold range. Like chromogenic substrate, the addition of dilution and heat treated plasma to the reaction resulted in an increase in optical density proportional to the concentration of plasma present. The presence of the treated plasma also resulted in an accelerated increase in optical density with comparable results when testing plasma at different concentrations and, additionally, serum. This accelerated increase in optical density may not be recognised in assays that monitor the progress of the reaction at a single time point and may confound assays of plasma samples that use chromogenic substrate. Plasma obtained from endotoxin sensitive and resistant strains of mice showed similar effects. The use of kinetic methodology means that a quantitative assay for endotoxin in plasma can be achieved, its variability comparable with that seen with semiquantitative serial dilution but with greater economy of the LAL reagent.

Epidemiological surveillance of Acinetobacter species.

Two hundred and sixty Acinetobacter isolates were recovered from 237 patients over a 2-year period; 156 isolates from 135 spinal cord injuries unit (SCIU) patients and 104 isolates from 102 patients in all the other hospital units. In SCIU patients, 133 isolates were recovered from the urine, 21 from wounds and aspirates, one from sputum and one from blood culture. In non-SCIU patients, 12 isolates were recovered from urine, 43 from wounds and aspirates, 48 from sputum and one from blood culture. Sixty-nine percent of isolates from SCIU patients showed resistance to gentamicin compared to 3% from non-SCIU patients. Gentamicin-resistant Acinetobacter anitratus was recovered from many environmental sites in the SCIU wards and from the hands of seven of 94 SCIU staff members tested. Serial rectal swabs were obtained from 79 newly-diagnosed SCIU patients. Ninety-two percent of those patients followed for up to 5 months acquired gentamicin-resistant Acinetobacter anitratus in their intestinal tract. API 2ONE profiles and antibiograms suggested that two distinct gentamicin-resistant strains of A. anitratus had become endemic in the SCIU and that nosocomial transmission was a frequent occurrence.

Methicillin-resistant Staphylococcus aureus in an Australian teaching hospital.

A survey was undertaken of all isolations of methicillin-sensitive and methicillin-resistant Staphylococcus aureus (MRSA) at a large Australian teaching hospital over a 12 month period. All methicillin-resistant isolations obtained from the Casualty and Outpatient clinics were from staff members or patients with recent hospital contact. Twenty per cent of all methicillin-resistant isolations from in-patients were from specimens taken within 2 days of the patient's admission. Each of these patients had had hospital contact within the previous 4 months and it is assumed that the majority of them reintroduced the organism into the hospital. Such patients may provide an important means by which infection control procedures are bypassed. Patients who were relatively more likely to become infected or colonized with methicillin-resistant than with methicillin-sensitive strains included the elderly and those with postoperative wound infections (especially after orthopaedic or vascular surgery), spinal injuries, peripheral vascular disease, chronic skin ulcers or chronic diseases of the respiratory or urinary tracts. Eleven per cent of MRSA wound isolates and 15 per cent of sputum isolates were associated with serious infections requiring specific treatment, emphasizing the ability of these strains to produce serious illness. A small proportion of staff and asymptomatic patients were found to harbour MRSA and the importance of these individuals in facilitating cross-infection requires further investigation.

A comparison of the susceptibilities of anaerobic bacteria to trimethoprim and sulfamethoxazole individually and in combination.

The activities of trimethoprim and sulfamethoxazole, singly and in combination, were compared with the activities of six other antimicrobial drugs against 50 anaerobic bacteria isolated from clinical specimens. Trimethoprim alone had little activity against the anaerobes tested, but sulfamethoxazole and the sulfamethoxazole/trimethoprim combination were active against most of the organisms. Results with the combination were slightly better than those with sulfamethoxazole alone.

Studies of herpes virus latency in the sensory spinal ganglia of rabbits.

Experimental latent herpes infection of rabbit dorsal root ganglia (DRG) is reported. The simian herpes virus used was derived from fatal natural infection in owl monkeys and has limited neurotropism in the rabbit. Following intradermal injection of the flank it causes a local lesion followed only by dorsal root ganglionitis; segmental paraesthesia and/or sensory loss going on to clinical recovery. Methods were developed for mapping sensory losses. Virus could be immediately re-isolated from skin or DRG homogenates in the acute (first week) stage but from 8-550 days by DRG organ culture only. Spontaneous recurrence does not occur but reactivation can be provoked. The system provides an improved analogue model for the study of the pathogenesis and symptomatic treatment of herpes zoster.

Intractable nasal carriage of methicillin-resistant Staphylococcus aureus.

The elimination of a methicillin-resistant strain of Staphylococcus aureus (MRSA) from the nose of a hospital staff member is described. Administration of antibacterial agents and intranasal inoculation of a sensitive strain of Staph. aureus failed to eradicate the MRSA. The MRSA disappeared after removal of the staff member from the hospital environment.

Antibiotics in immunosuppressed patients.

The initial treatment of an infection in an immunosuppressed patient must be aimed at the most commonly involved microorganisms which may result in a rapidly fatal infection. As soon as a microbiological diagnosis had been made, the treatment should be altered if necessary to provide optimal management of the condition.

Hazards from simian herpes viruses: reactivation of skin lesions with virus shedding.

A new simian herpes virus with biological properties similar to herpes simplex and to simian "B" virus has been used as a model system for studying virus latency in dorsal root spinal sensory ganglia. Following intradermal injection, virus is present in the skin lesions and corresponding ganglia only, during the acute stage of the disease. By organ-culture techniques, latent virus was rescued from ganglia up to 2 years later. No latent virus was ever found in skin organ cultures of the primary site. Treatment with cortisone up to 18 months later reactivated virus latent in the ganglia, and virus returned to the skin where it produced small but typical herpes lesions which shed virus. Reactivation of Herpesvirus tamarinus was achieved after 28 months. This is believed to be the first report of a model system for the study of herpes latency in which skin lesions are found to recur, and provides an opportunity for more detailed investigations of the mechanisms of virus latency in man. The presumption that reactivation of skin lesions will also be possible in rhesus monkeys seropositive for "B" virus points to a possibly grave and largely unsuspected hazard for those engaged in primate research.